The invention relates to a subperiosteal jaw implant and to a method for manufacturing such an implant.
The invention relates to an assembly of a jaw implant for oral subperiosteal placement of a dental prosthesis over the alveolar ridge of a patient's maxilla or mandible, and of column-shaped supports for supporting the dentures on the jaw implant. The invention further relates to placing such an assembly.
Subperiosteal implants are used in oral and maxillofacial surgery, including dentistry, when a patient is suffering from partial or complete edentulism or advanced bone atrophy and needs to wear a dental prosthesis. After the jaw bone has temporarily been stripped of the gingiva and mucosa, the implant is attached to the jaw bone that is still present by means of screws. The implant forms an endo-prosthesis, to which, via transmucosal/transgingival supports, usually in the form of columns or pillars, the actual dental prosthesis or dentures, the exo-prosthesis, is attached.
Subperiosteal jaw implants are used if bone grafting, an alveolar ridge augmentation or sinus lift is not an option or inconvenient.
In an old technique (Weinberg) a grid-shaped plate was bent in accordance with the shape of the jaw bone and cut to size and finished. Subsequently a supporting column for the endo-prosthesis was soldered onto the plate situated underneath the bone membrane, which plate was bent on both sides of the alveolar ridge like a saddle. The soft tissue was then placed back again and sutured. The intention was that the plate would follow the contours of the supporting bone and the fit would contribute to the stability. However, this often turned out not to be the case.
Goldberg and Gerhkoff had a different approach, wherein an impression was made of the jaw, over the soft tissue and an estimate of the tissue thickness was made by means of X-rays and palpation, on the basis of which data a plaster model of the jawbone was made. Based on said model a molded piece out of Vitallium (a chromium-cobalt-molybdenum alloy) was made, with support columns thereon, formed as one unity therewith. The tissue on the bone was incised and laid aside, after which the molded piece was placed on the exposed bone and attached thereto using vertical screws. The soft tissue was then sutured again. In this case as well, the stability often turned out inadequate in the long term due to the inaccurate fit and peri-implantitis due to failing gingival-adhesion to the metal.
Berman, Lew, Marziani and others started from an impression of the exposed alveolar ridge for a better fit. Berman made a plaster model in the image of the impression. From the stone model he cast a grid-shaped implant made of Vitallium that was attached using tantalum wires. Marzani made a plaster compression mold from the impression, in which mold a wire mesh or grid-shaped plate made of tantalum was pressed into the right shape. Support columns were soldered or screwed secure to the implant. The implant was then attached to the jaw bone using screws on the exterior inclined areas of the alveolar ridge and on the symphysis.
Making an impression of the alveolar ridge after making an incision into the soft tissue and laying it aside, is very trying for a patient. Furthermore, the long period passing between making the impression and placing the implant during a second surgical session is also onerous.
A further drawback in existing techniques and subperiosteal implants is the problem that in case of failing gingival adhesion, gingivitis may arise around the pillars between the implant and the prosthesis, the gingivitis spreading along the pillar in a direction towards the implant and possibly resulting in peri-implantitis, bone decay, in the area surrounding and underneath the implant. This may result in a bone crater and in case of spreading may cause a perforation towards the sinus, the nose, the canalis mandibularis. Further ingrowing epithelium may result in the entire frame getting detached from the bone.